| . Statement from the Eighth Climate Outlook Forum for the Greater Horn of Africa . |
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27--30 August 2001, Jinja, Uganda Summary There is increased likelihood of near-normal rainfall over most of the Greater Horn of Africa sub-region for the period September - December 2001. However, probabilities are favouring above-normal rainfall over southern Sudan, northwestern Uganda and western Ethiopia and below normal rainfall over eastern Eritrea, extreme southern Ethiopia, northeastern Uganda, much of Kenya, southwestern Somalia and central and much of northern Tanzania. It should be recalled that some parts of the sub-region have experienced drought conditions for the past several seasons. Below normal rainfall conditions are again, more likely for some of these areas. The impacts of the accumulated rainfall deficits may therefore be exacerbated. The outlook is relevant only for seasonal time scales and relatively large areas. Local and month-to-month variations may occur. It has been noted that Sea Surface Temperatures (SSTs) in tropical eastern Pacific are near normal and the development of SST anomalies in Indian and Atlantic Oceans are still uncertain. It should also be noted that part of the forecast period coincides with the start of the formation of tropical cyclones over the southwestern Indian Ocean. These may influence the patterns of rainfall anomalies in the sub region towards the end of the season. The users are therefore strongly advised to keep in contact with their National Meteorological Services for interpretation of this outlook, finer details, updates and additional guidance. The Climate Outlook Forum From 27 to 30 August 2001, the eighth Climate Outlook Forum was convened in Jinja, Uganda by the Drought Monitoring Centre, Nairobi (DMCN) to formulate consensus guidance for the September to December 2001 season in the Greater Horn of Africa (sometimes referred to as the eastern Africa sub region, comprising of Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, Sudan, Tanzania and Uganda). Potential users were active participants in the forum. They helped to develop the outlook and assisted in identifying the implications for the respective countries and sectors. The forum reviewed the state of the global climate system and its implications for the sub-region. Among the principal factors taken into account were the observed and predicted SSTs in the tropical Pacific Ocean and over much of the tropical Atlantic and Indian Oceans. Methodology The forum examined the decay of 1998-2000 La Nina episode and the current and expected near average SSTs over the Pacific Ocean as well as the SST anomalies over the Indian and Atlantic Oceans together with other factors that affect the climate of the sub region. These factors were assessed using coupled ocean-atmosphere models, statistical models and expert interpretation. The current status of seasonal to inter-annual forecasting allows prediction of spatial and temporal averages and may not fully account for the physical and dynamical factors that influence regional and national climate variability. The experts established probability distributions to indicate the likelihood of above-, near, or below-normal rainfall for each zone (see Map). Above-normal rainfall is defined as within the wettest third of recorded rainfall amounts in each zone; near normal is defined as the third centred around the climatological median; below normal rainfall as within the driest third of the rainfall amounts. Outlook September to December constitutes an important rainfall season over the Greater Horn of Africa sub-region. However, the dry season begins after September in northern Sudan, northern Ethiopia and parts of Eritrea. The rainfall outlook for each zone within this sub-region is given below. Greater Horn of Africa Consensus Climate Outlook for the period September to December 2001 Zone I: Increased likelihood of near normal to below normal rainfall over Tanzania coast, Kenyan coast and southern coast of Somalia. Zone II: Increased likelihood of below normal to near normal rainfall over central and much of northern Tanzania, much of Kenya, northeastern Uganda, extreme southern Ethiopia and southwestern Somalia. Zone III: Increased likelihood of near normal to above normal rainfall over Burundi, Rwanda, southern and western Tanzania, central and southern Uganda and western Kenya. Zone IV: Increased likelihood of above normal to near normal rainfall over northwestern Uganda, southern and central Sudan and western Ethiopia. Zone V: Increased likelihood of near normal to above normal rainfall over much of Ethiopia, central and northern Somalia, Djibouti, much of Eritrea and northern Sudan. Zone VI: Increased likelihood of below normal to near normal rainfall over eastern and northern Eritrea. Note: The numbers for each zone indicate the probabilities (chances of occurrence) of rainfall in each of the three categories, above-, near-, and below normal. The top number indicates the probability of rainfall occurring in the above-normal category; the middle number is for the near normal and the bottom number for the below-normal category. For example, in case of Tanzania coast, Kenyan coast and southern coast of Somalia (zone I), there is 25% probability of rainfall occurring in the above normal category; 40% probability of rainfall occurring in the near-normal category; and 35% probability of rainfall occurring in the below normal category. It is emphasized that boundaries between zones should be considered as transition areas (view map). Contributors: The eighth climate outlook forum for the Greater Horn of Africa
was organised jointly by the Drought Monitoring Centre, Nairobi (DMCN),
World Meteorological Organisation (WMO) and the International Research
Institute for climate prediction (IRI) within the framework of the United
States Agency for International Development (USAID) funded project,
“Applications of meteorology to the reduction of climate and weather
related risks to food security, water resources, and health for sustainable
development in the Greater Horn of Africa sub-region”. |
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